Process for the application of a transparent metal oxide layer on a film

Abstract

A pure metal is vaporized in a receiver, and a quantity of oxygen slightly substoichiometric for the oxide is introduced. To determine the thickness of the layer deposited on the film and to control the vaporization rate, optical sensors are installed in an area where the layer, because of the presence of unoxidized metal, has sufficient absorption for optical measurement. After the determination of the transparency by the sensors, the layer is subjected to a secondary oxidation process.

What is claimed is:  
     
       1. Process for applying a transparent metal oxide on a film, comprising 
       passing a film through a receiver,  
       vaporizing metal in said receiver to produce vapor phase metal,  
       introducing oxygen into said receiver in order to produce a metal oxide layer on said film, said oxygen being introduced in an amount which is not sufficient to produce a stoichiometric metal oxide layer on said film, whereby said layer is not completely transparent, said layer having an absorption coefficient,  
       measuring the absorption coefficient of said layer using optical sensors, said absorption coefficient providing a means for determining thickness of the layer,  
       controlling the rate of vaporizing metal based on the absorption coefficient, and  
       subjecting the layer to further oxidation in order to produce a stoichiometric oxide which is fully transparent.  
     
     
       2. Process as in claim  1  wherein said layer is subjected to secondary oxidation by exposure to air outside of said receiver. 
     
     
       3. Process as in claim  1  wherein said layer is subjected to secondary oxidation by an oxidation stage downstream of said optical sensors. 
     
     
       4. Process as in claim  1  wherein said metal is vaporized by passing an electron beam over a crucible containing said metal, said beam has a power, and said metal is vaporized at a rate which is controlled by adjusting the power of the electron beam as a function of the absorption coefficient. 
     
     
       5. Process as in claim  1  wherein said metal is aluminum. 
     
     
       6. Process as in claim  1  wherein a plasma is generated in the receiver. 
     
     
       7. Process as in claim  1  wherein microwave energy is introduced into said vapor phase metal. 
     
     
       8. Process as in claim  1  wherein said absorption coefficient is measured at plural points across the width of the film, and wherein said metal is vaporized by moving an electron beam over a crucible containing said metal, said beam having a power, said metal being vaporized at a rate which is controlled by at least one of adjusting power and adjusting movement of the electron beam based on absorption coefficients at said plural points.